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Abstract:

A biometric authentication device that authenticates a user using
biological features of the user, the biometric authentication device
includes: an illumination unit configured to illuminate a target which
represents the biological features; an image sensor configured to obtain
a first captured image by capturing the target illuminated by the
illumination unit, and obtain a second captured image by capturing the
target not illuminated by the illumination unit; an acquisition unit
configured to acquire from a storage unit a mask which has a target area
approximating the shape of the target in the first and second captured
images obtained by the image sensor; and a detection unit configured to
detect light other than illumination light illuminated by the
illumination unit based on the mask acquired by the acquisition unit and
at least one of the first and second images.

Claims:

1. A biometric authentication device that authenticates a user using a
biological feature of the user, the biometric authentication device
comprising: an illumination unit configured to illuminate a target which
represents the biological feature; an image sensor configured to obtain a
first captured image by capturing the target illuminated by the
illumination unit, and obtain a second captured image by capturing the
target not illuminated by the illumination unit; an acquisition unit
configured to acquire from a storage unit a mask which has a target area
approximating a shape of the target in the first and second captured
images obtained by the image sensor; and a detection unit configured to
detect light other than illumination light illuminated by the
illumination unit based on the mask acquired by the acquisition unit and
at least one of the first and second images.

2. The biometric authentication device according to claim 1, wherein the
detection unit detects incident light which directly enters the image
sensor in the light other than the illumination light based on brightness
of an area other than the target area in the first and second captured
images.

3. The biometric authentication device according to claim 2, wherein the
detection unit detects a fluctuation of the incident light based on the
first and second captured images and first and second captured images
captured with timing different from timing of the first and second
captured images.

4. The biometric authentication device according to claim 1, wherein the
detection unit detects light which enters the image sensor by being
reflected by the target in the light other than the illumination light
based on brightness in the target area in the second captured image.

5. The device according to claim 1, wherein the detection unit detects
light which enters the image sensor by being reflected by an object other
than the target in light other than the illumination light based on
brightness of pixels outside the target area and contacting the target
area in the first and second captured images.

6. A computer-readable recording medium having stored therein a biometric
authentication program for causing a computer to execute a procedure, the
procedure comprising: illuminating by an illumination unit a target which
represents the biological feature; obtaining by an image sensor a first
captured image by capturing the target illuminated by the illumination
unit, and obtaining a second captured image by capturing the target not
illuminated by the illumination unit; acquiring from a storage unit a
mask which has a target area approximating a shape of the target in the
first and second captured images; and detecting light other than
illumination light illuminated by the illumination unit based on the
acquired mask and at least one of the first and second images.

7. The computer-readable recording medium according to claim 6, wherein
the detecting includes detecting incident light which directly enters the
image sensor in the light other than the illumination light based on
brightness of an area other than the target area in the first and second
captured images.

8. The computer-readable recording medium according to claim 7, wherein
the detecting including detecting a fluctuation of the incident light
based on the first and second captured images and first and second
captured images captured with timing different from timing of the first
and second captured images.

9. The computer-readable recording medium according to claim 6, wherein
the detecting includes detecting light which enters the image sensor by
being reflected by the target in the light other than the illumination
light based on brightness in the target area in the second captured
image.

10. The computer-readable recording medium according to claim 6, wherein
the detecting includes detecting light which enters the image sensor by
being reflected by an object other than the target in light other than
the illumination light based on brightness of pixels outside the target
area and contacting the target area in the first and second captured
images.

11. A biometric authentication method for causing a computer to
authenticate a user using a biological feature of the user, the biometric
authentication method comprising: illuminating by an illumination unit a
target which represents the biological features; obtaining by an image
sensor a first captured image by capturing the target illuminated by the
illumination unit, and obtaining a second captured image by capturing the
target not illuminated by the illumination unit; acquiring from a storage
unit a mask which has a target area approximating a shape of the target
in the first and second captured images; and detecting light other than
illumination light illuminated by the illumination unit based on the
acquired mask and at least one of the first and second images.

12. The biometric authentication method according to claim 11, wherein
the detecting includes detecting incident light which directly enters the
image sensor in the light other than the illumination light based on
brightness of an area other than the target area in the first and second
captured images.

13. The biometric authentication method according to claim 12, wherein
the detecting includes detecting a fluctuation of the incident light
based on the first and second captured images and first and second
captured images captured with timing different from timing of the first
and second captured images.

14. The biometric authentication method according to claim 11, wherein
the detecting includes detecting light which enters the image sensor by
being reflected by the target in the light other than the illumination
light based on brightness in the target area in the second captured
image.

15. The biometric authentication method according to claim 11, wherein
the detecting includes detecting light enters the image sensor by being
reflected by an object other than the target in light other than the
illumination light based on brightness of pixels outside the target area
and contacting the target area in the first and second captured images.

Description:

CROSS-REFFERENCE TO RELATED APPLICATION

[0001] This application is a continuation application of International PCT
Application No. PCT/JP2010/055519, filed on Mar. 29, 2010, the entire
contents of which are incorporated herein by reference.

FIELD

[0002] The technology disclosed in this specification relates to a
biometric authentication device, a biometric authentication program, and
a biometric authentication method.

BACKGROUND

[0003] Biometric authentication for identity verification which is
performed by capturing a biological feature of a user with a camera and
comparing the feature with a registration template as the user biological
feature registered in advance is known as a authentication technique for
identity verification. In order to capture an image appropriate for the
authentication, the biometric authentication device for performing the
biometric authentication includes a mechanism of adjusting the exposure
of the camera and the intensity of the illumination provided for the
biometric authentication device depending on the intensity of the
external light to an object to be captured. In addition, the technology
of surveying the installation environment of the biometric authentication
device relating to the illumination when the registration template is
registered or when the biometric authentication is performed, adjusting
an image based on the result of the survey, and issuing a warning to a
user is known.

[0004] However, according to the technology above, there is the problem
that the result of the survey is subject to the influence from the
fluctuation of the biological feature because the biological feature of a
user is used in the survey of the installation environment of the
biometric authentication. The fluctuation of the biological feature can
be caused by a change of the state of the biological feature, and the
displacement of the presentation position to the device.

[0007] According to as aspect of the embodiments, a biometric
authentication device that authenticates a user using a biological
feature of the user, the biometric authentication device includes: an
illumination unit configured to illuminate a target which represents the
biological feature; an image sensor configured to obtain a first captured
image by capturing the target illuminated by the illumination unit, and
obtain a second captured image by capturing the target not illuminated by
the illumination unit; an acquisition unit configured to acquire from a
storage unit a mask which has a target area approximating a shape of the
target in the first and second captured images obtained by the image
sensor; and a detection unit configured to detect light other than
illumination light illuminated by the illumination unit based on the mask
acquired by the acquisition unit and at least one of the first and second
images.

[0008] The object and advantages of the invention will be realized and
attained by means of the elements and combinations particularly pointed
out in the claims.

[0009] It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory and
are not restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

[0010] FIG. 1 is a configuration of the hardware of the biometric
authentication device according to an embodiment of the present
invention;

[0011] FIG. 2 is a configuration of the hardware of the capture unit;

[0012] FIG. 3 illustrates an evaluation target;

[0013] FIG. 4 is a configuration of the functions of the biometric
authentication device according to an embodiment of the present
invention;

[0014] FIG. 5 illustrates an operation of the surveying process of the
installation environment;

[0015] FIG. 6 is an ideal ON image;

[0016] FIG. 7 is an ideal OFF image;

[0017] FIG. 8 illustrates the external light and undesired capturing in
the ON image;

[0018] FIG. 9 illustrates the external light, undesired capturing, and
reflection in the OFF image;

[0019] FIG. 10 illustrates the survey result information; and

[0020] FIG. 11 is an example of a computer system.

DESCRIPTION OF EMBODIMENTS

[0021] The embodiment of the present invention is described below with
reference to the attached drawings.

[0022] The hardware configuration according to the present embodiment is
first described below. FIG. 1 is a configuration of the hardware of the
biometric authentication device according to an embodiment of the present
invention. FIG. 2 is a configuration of the hardware of the capture unit.
FIG. 3 illustrates an evaluation target.

[0023] A biometric authentication device 1 according to the present
embodiment performs vein authentication on the palm of a user, and
surveys an installation environment. As illustrated in FIG. 1, the
biometric authentication device 1 includes a CPU (Central Processing
Unit) 10, memory 11, non-volatile memory 12, a display 13, an input unit
14, and a capture unit 15. The CPU 10 controls the biometric
authentication device 1. The memory 11 is a main memory directly accessed
by the CPU 10. The non-volatile memory 12 stores a user ID and a
registration template corresponding to the user ID, a first threshold, a
second threshold, a third threshold, a fourth threshold, and an
evaluation mask described later. It is assumed that each of the first
through fourth thresholds is a parameter relating to the survey of the
installation environment, has two values, and is determined based on the
capture result in a standard environment. The non-volatile memory 12 can
be a hard disk, flash memory, etc. The display 13 presents information to
the user of the biometric authentication device 1. The input unit 14 is
equipment with which the user of the biometric authentication device 1
inputs an ID. The input unit 14 can be a ten-key keypad, a keyboard, a
touch panel, a reader of non-contact IC card on which an ID is recorded,
etc.

[0024] As illustrated in FIG. 2, the capture unit 15 includes a casing
161, a guide 162, an illumination unit 163, and a camera 164. The guide
162 is provided on the casing, and introduces the palm of a user to the
appropriate image-capturing position. The illumination unit 163 emits a
near-infrared light to the palm of a user. The illumination unit 163 can
be an LED. The sensor 164 receives the near-infrared light emitted from
the illumination unit 163 and reflected by the palm, thereby capturing
the vein image of the palm. The sensor 164 also captures the area
including the palm and its vicinity. The sensor 164 can be a CMOS
(Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge
Coupled Device) image sensor, etc.

[0025] In addition, the biometric authentication device 1 surveys the
installation environment using an evaluation target as illustrated in
FIG. 3. The survey of the installation environment is made on four items,
that is, the reflection, the intensity of the external light, the time
change of the external light, and the undesired capturing. The reflection
refers to a state in which the external light reflected by the casing
161, the desk, the wall, etc. in the vicinity of the biometric
authentication device 1 illuminates the palm. The intensity of the
external light refers to an intensity of the external light such as the
sunlight, the illumination of an installation environment, etc. directly
entering the sensor 164. The time change of the external light refers to
a case in which the external light changes in a short time interval, for
example, by opening and closing a blind near the biometric authentication
device 1. The undesired capturing refers to a state in which an object
other than the palm excluding the guide is captured near the palm and it
is difficult to discriminate the object from the palm in the image. The
evaluation target has an average feature of the palm as a biological
feature. In particular, the evaluation target is generated based on the
average of a plurality of palms relating to the shape, size, and
reflectance. In addition, it is assumed that the evaluation target is
fixed to a constant position relative to the sensor 164 by the guide 162.
It is also assumed that the evaluation target has a plane approximating
the shape of the averaged palm in a two-dimensional pattern. The
evaluation target can be a three-dimensional pattern representing the
average palm.

[0026] Described next is the configuration of the functions of the
biological authentication device according to the present embodiment.
FIG. 4 illustrates a configuration of the functions of the biological
authentication device according to the present embodiment.

[0027] As illustrated in FIG. 4, the biometric authentication device 1
includes as the functions a capture control unit 21, a mask acquisition
unit 22, a first calculation unit 23, a second calculation unit 24, a
setting unit 25, a third calculation unit 26, a fourth calculation unit
27, a score recording unit 28, a score display unit 29, an extraction
unit 30, and a comparison unit 31. These functions are realized by the
cooperation of the CPU 10 and the memory 11. The capture control unit 21
controls the capturing using the sensor 164, and the illumination unit
163 relating to the capturing. The mask acquisition unit 22 acquires an
evaluation mask from the non-volatile memory 12. The evaluation mask
indicates the target area as an area approximating the position and shape
of the evaluation target in the captured image. The first calculation
unit 23 calculates a reflection score as a parameter relating to the
reflection using a first threshold. The second calculation unit 24
calculates an external light score as a parameter relating to the
intensity of the external light using a second threshold. The setting
unit 25 adjusts the sensibility of the sensor 164 and the quantity of
illumination light of the illumination unit 163 based on the reflection
score and the external light score. The third calculation unit 26
calculates an external light fluctuation score as a parameter relating to
the change of the external light using a third threshold. The fourth
calculation unit 27 calculates an undesired capturing score as a
parameter relating to the undesired capturing using a fourth threshold.
The score recording unit 28 records each score calculated by the first
calculation unit 23, the second calculation unit 24, the third
calculation unit 26, and the fourth calculation unit 27 in the
non-volatile memory 12. The score display unit 29 displays each
calculated score, and displays a message to a user based on each score.
The extraction unit 30 extracts a vein pattern as a biological feature
from the image of the palm captured by the sensor 164. The comparison
unit 31 compares the registration template corresponding to the ID input
to the input unit 14 with the vein pattern extracted by the extraction
unit 30, and authenticates the user.

[0028] Described next is the operation of the surveying process of the
installation environment of the biometric authentication device according
to the present embodiment. FIG. 5 illustrates an operation of the
surveying process of the installation environment. FIG. 6 is an ideal ON
image. FIG. 7 is an ideal OFF image. FIG. 8 illustrates the external
light and undesired capturing in the ON image. FIG. 9 illustrates the
external light, undesired capturing, and reflection in the OFF image.
FIG. 10 illustrates the survey result information. In FIG. 5, it is
assumed that the biometric authentication device is installed in the
place where the biometric authentication is performed on a user, and an
evaluation target is set in the casing of the capture unit.

[0029] As illustrated in FIG. 5, the capture control unit 21 first turns
on the illumination by the illumination unit 163 and captures the
evaluation target as a first ON image (S101), and then turns off the
illumination and captures the evaluation target as the first OFF image
(S102). When there is no external light, undesired capturing, or
reflection, the ON image as an image captured when the illumination is
turned on is illustrated in FIG. 6, and the OFF image as an image
captured when the illumination is turned off is illustrated in FIG. 7.
These ON and OFF images illustrated in FIGS. 6 and 7 are appropriate for
the biometric authentication. On the other hand, when there is external
light, undesired capturing, or reflection, the ON image can be
illustrated as FIG. 8, and the OFF image can be illustrated as FIG. 9.

[0030] Next, the mask acquisition unit 22 acquires an evaluation mask from
the non-volatile memory 12 (S103), and the first calculation unit 23
calculates the reflection score based on the first OFF image and the
evaluation mask (S104). In particular, the first calculation unit 23
calculates an average of the brightness of the 5% pixels in descending
order of the brightness of the pixels within the evaluation mask area in
the first OFF image, compares the average with the first threshold, and
determines the reflection score based on the comparison result. In the
present embodiment, the brightness is expressed by 256 scales of 0
through 255. Relating to the brightness, the first threshold has two
values of 40 and 70. The reflection score is A when the average of the
brightness is less than 40, B when it is equal to or more than 40 and
less than 70, and C when it is equal to or more than 70. A indicates no
reflection, B indicates reflection detected, and C indicates reflection
higher than B. Other scores are also expressed by three stages of A
through C.

[0031] Next, the second calculation unit 24 calculates the external light
score based on the first ON image and the first

[0032] OFF image (S105). In particular, the second calculation unit 24
calculates an average of the 5% pixels in descending order of the
brightness of the pixels in the area outside the evaluation mask area in
the first ON image and the first OFF image, compares the average with the
second threshold, and determines the external light score based on the
comparison result. In the present embodiment, the second threshold has
two values of 60 and 80. The external light score is A when the
brightness average is less than 60, B when it is equal to or more than 60
and less than 80, and C when it is equal to or more than 80. A indicates
no external light, B indicates the existence of external light, and C
indicates the external light higher than B.

[0033] Next, the setting unit 25 adjusts the sensitivity of the sensor 164
and the quantity of illumination light of the illumination unit 163 based
on the calculated reflection score and external light score (S106). After
the adjustment, the capture control unit 21 turns on the illumination by
the illumination unit 163 and captures the evaluation target as the
second ON image (S107), and next turns off the illumination and captures
the evaluation target as the second OFF image (S108). Then, the capture
control unit 21 determines whether or not a specified time has passed
since the second OFF image was captured (S109).

[0034] When the specified time has passed (YES in S109), the capture
control unit 21 turns on the illumination by the illumination unit 163
and captures the evaluation target as the third ON image (S110), and next
turns off the illumination and captures the evaluation target as the
third OFF image (S111). Next, the third calculation unit 26 calculates
the external light fluctuation score based on the second ON image, the
second OFF image, the third ON image, and the third OFF image (S112). In
particular, relating to the brightness, the second calculation unit 24
compares the second ON image with the third ON image, and the second OFF
image with the third OFF image, and calculates the number of pixels
having the brightness difference which is equal to or more than a
specified value at the same positions in the pixels outside the target
area and not contacting the target area in the two comparing processes
above. Furthermore, the third calculation unit 26 compares the number of
pixels with the third threshold. In the present embodiment, the third
threshold has two values of 1000 and 2000. The external light fluctuation
score is A when the number of pixels is less than 1000, B when it is
equal to 1000 or more and less than 2000, and C when it is equal to 2000
or more. A indicates no external light fluctuation, B indicates external
light fluctuation detected, and C indicates higher external light
fluctuation than B.

[0035] Next, the fourth calculation unit 27 calculates the undesired
capturing score based on the second ON image, the second OFF image, the
third ON image, and the third OFF image (S113). In particular, relating
to the brightness, the fourth calculation unit 27 compares the second ON
image with the second OFF image, and the third ON image with the third
OFF image, and calculates the number of pixels having the brightness
difference which is equal to or more than a specified value at the same
positions in the pixels outside the target area and contacting the target
area in the two comparing processes above. Furthermore, the fourth
calculation unit 27 compares the number of pixels with the fourth
threshold. In the present embodiment, the fourth threshold has two values
of 1000 and 2000. The undesired capturing score is A when the number of
pixels is less than 1000, B when it is equal to 1000 or more and less
than 2000, and C when it is equal to 2000 or more. A indicates no
undesired capturing, B indicates undesired capturing detected, and C
indicates higher undesired capturing than B.

[0036] Next, the score recording unit 28 records the calculated reflection
score, external light score, external light fluctuation score, and
undesired capturing score as the survey result information as illustrated
in FIG. 10 in the non-volatile memory 12 (S114). Relating to the external
light and the undesired capturing, the score recording unit 28 can record
the position of the pixel exceeding the threshold as the survey result
information. After the recording process, the score display unit 29
displays the reflection score, the external light score, the external
light fluctuation score, and the undesired capturing score on the display
13 according to the survey result information (S115). In addition, when
there is an item having a low score, the score display unit 29 displays a
message requesting an improvement on the display 13. The score display
unit 29 can also display the positions of the external light and the
undesired capturing on the display 13.

[0037] In step S109, when the specified time has not passed (NO in S109),
the capture control unit 21 determines again whether or not the specified
time has passed, and passes control to the next step (S110).

[0038] As described above, according to the present embodiment, the
influence of the fluctuation from the biological feature can be excluded
in the survey of the installation environment using the evaluation
target. In addition, according to the present embodiment, the area of the
palm to be authenticated can be more correctly discriminated from the
other areas using the evaluation mask approximating the evaluation
target. Therefore, a more correct value can be calculated relating to the
survey of the installation environment. In the present embodiment, the
biometric authentication device 1 is to authenticate the vein of a palm,
but it is also to perform other biometric authentication. In addition,
each score is expressed by three stages of A through C, but can be
expressed by any number of stages so far as it is expressed by two or
more stages. When there are two stages for each score, it indicates
whether or not the light other than the light illuminated by the
illumination unit 163 (illumination light) has been detected. That is,
the first calculation unit 23, the second calculation unit 24, the third
calculation unit 26, and the fourth calculation unit 27 according to the
present embodiment detect the light other than the illumination light and
calculate the level of the detected light.

[0039] The technology disclosed by the present specification can be
applied in the computer system described below by connecting biometric
authentication equipment. FIG. 11 is an example of a computer system to
which the technology disclosed in the present specification is applied. A
computer system 900 illustrated in FIG. 11 includes a body unit 901
containing a CPU, a disk drive, etc., a display 902 for displaying an
image at an instruction from the body unit 901, a keyboard 903 for
inputting various types of information to the computer system 900, a
mouse 904 for specifying any position on a display screen 902a of the
display 902, and a communication device 905 for accessing an external
database etc. to download a program etc. stored in another computer
system. The communication device 905 can be a network communication card,
a modem, etc.

[0040] A program for directing the above-mentioned computer system to
execute each of the above-mentioned steps can be provided as a biometric
authentication program. The program can be executed by a computer system
configuring a biometric authentication device by storing the program in a
recording medium readable by a computer system. The program for executing
each of the above-mentioned steps is stored in a portable recording
medium such as a disk 910 etc. or downloaded from a recording medium 906
of another computer system by the communication device 905. In addition,
the biometric authentication program (biometric authentication software)
which assigns at least the biometric authentication function to the
computer system 900 is input to the computer system 900 and compiled. The
program operates the computer system 900 as a biometric authentication
device having the biometric authentication function. In addition, the
program can be stored in a computer readable recording medium such as the
disk 910 etc. The recording medium readable by the computer system 900
can be a built-in storage device in a computer such as ROM, RAM, etc., a
portable storage medium such as the disk 910, a flexible disk, a DVD
disk, a magnetic optical disk, an IC card, etc., a database holding a
computer program, other computer systems and their databases, and various
recording media accessible by a computer system connected through a
communication device such as the communication device 905.

[0041] All examples and conditional language provided herein are intended
for the pedagogical purposes of aiding the reader in understanding the
invention and the concepts contributed by the inventor to further the
art, and are to be construed as limitations to such specifically recited
examples and conditions, nor does the organization of such examples in
the specification relate to a showing of the superiority and inferiority
of the invention. Although one or more embodiments of the present
invention have been described in detail, it should be understood that the
various changes, substitutions, and alterations could be made hereto
without departing from the spirit and scope of the invention.